Re: [Harp-L] Double Reed Plate Harmonicas

[Vern <jevern@xxxxxxx>]

> On Apr 9, 2016, at 12:26 PM, Tom Halchak <info@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> 
> ââ.The question about compression is mostly parsing wordsââ..
It is indeed. Until we agree on what it means, the word is useless in a harmonica discussion.  To me, it means crowding the air molecules together to raise the pressure.  However, I donât think that is what it means to harmonica players.  I keep asking what it means to you guys but get no answers.

>  â.We all agree that thicker reed plates effectively increases the volume of air in the chambers formed by the reed slotsâ..
The slot is not an isolated chamber.  The part of the slot inside the reed is part of the comb chamber and arguably also part of the playerâs embouchure.  The part of the slot outside the reed is part of the volume under the cover and arguably also part of the room volume. In both cases, the portions of the total volumes contributed by the slot is minuscule.

> â.Each time the reed swings through the slot it moves more airâ.
The air moves the reed, not vice versa. With a thicker plate, a larger part of the vibration cycle occurs in the slot.  The longer the reed remains in the slot,  the less air moves through it.  Think of the reed not as a piston but as a valve, allowing or cutting off flow through the slot.  For short reeds that donât emerge from the back side of a single plate, the second plate may have no effect.

> â.Nobody has disputed the notion that it results in a harmonica that is louderâ.
I will dispute it here.  This is an area where confirmation bias is likely to affect human perception.  To establish this as fact, you need to blow a number of otherwise-identical harps with single and double plates by an air pump and measure loudness with a sound meter.  The logarithmic response of the human ear requires a very large difference in sound energy to be perceptible.  

>   â.If you bore out the cylinders on an engine to make them larger, it increases the displacement and raises compression.
> Why would the same principle not apply to a reed plate?...
Because the cylinder is closed and the slot is open.  Think of the engine with the cylinder head and the crank-case removed. 

Your claims could possibly be true.  However, your explanation doesnât make sense to me.

Vern